Controversial crypto technology known as Dual EC DRBG, thought to be a backdoor for the National Security Agency, ended up in some Cisco products as part of their code libraries. But Cisco says they cannot be used because it chose other crypto as an operational default which can't be changed.

Dual EC DRBG or Dual Elliptic Curve Deterministic Random Bit Generator (Dual EC DRBG) from the National Institute of Standards and Technology and a crypto toolkit from RSA is thought to have been one main way the crypto ended up in hundreds of vendors' products.

Because Cisco is known to have used the BSAFE crypto toolkit, the company has faced questions about where Dual EC DRBG may have ended up in the Cisco product line. In a Cisco blog post today, Anthony Grieco, principle engineer at Cisco, tackled this topic in a notice about how Cisco chooses crypto.

"Before we go any further, I'll go ahead and get it out there: we don't use the Dual_EC_DRBG in our products. While it is true that some of the libraries in our products can support the DUAL_EC_DRBG, it is not invoked in our products."

Grieco wrote that Cisco, like most tech companies, uses cryptography in nearly all its products, if only for secure remote management.

"Looking back at our DRBG decisions in the context of these guiding principles, we looked at all four DRBG options available in NIST SP 800-90. As none had compelling interoperability or legal implementation implications, we ultimately selected the Advanced Encryption Standard Counter mode (AES-CTR) DRBG as out default."

Grieco stated this was "because of our comfort with the underlying implementation, the absence of any general security concerns, and its acceptable performance. Dual_EC_DRBG was implemented but wasn't seriously considered as the default given the other good choices available."

Grieco said the DRBG choice that Cisco made "cannot be changed by the customer."

Faced with the Dual EC DRBG controversy, which was triggered by the revelations about the NSA by former NSA contractor Edward Snowden, NIST itself has re-opened comments about this older crypto standard.

"The DRBG controversy has brought renewed focus on the crypto industry and the need to constantly evaluate cryptographic algorithm choices," Grieco wrote in the blog today. "We welcome this conversation as an opportunity to improve security of the communications infrastructure. We're open to serious discussions about the industry's cryptographic needs, what's next for our products, and how to collectively move forward." Cisco invited comment on that online.

Grieco concluded, "We will continue working to ensure out products offer secure algorithms, and if they don't, we'll fix them."